Phosphorane polyesters and polyamides

ABSTRACT

Bis(halophosphoranes) react with diamines or dihydroxy compounds to give phosphorane polyamides or polyesters respectively.

United States Patent [15] 3,674,742

Baldwin et al. July 4, 1972 [54] PHOSPHORANE POLYESTERS AND 58 Field ofSearch ..260/47 P POLYAMIDES [56] References Cited [72] Inventors: RogerA. Baldwin, La Mirada; Ming T.

Cheng, Buena Park, both of Calif. UNITED STATES PATENTS [73] Assignee:Kerr McGee Chemical Corp. 3,227,685 l/l966 Nielsen et al. 260/473,341,477 9/1967 Washburn et al ..260/2 Filed: w- 24, 1970 3,402,1459/1968 Hull el al. ..260/54 [21] ApplNo': 75283 Primary Examiner-MelvinGoldstein Related USI pp Data Attorney-William G. Addison [62] Divisionof Ser. No. 793,630, Nov. 12, 1968, Pat. No. [57] ABSTRACT 3,629,296-Bis(halophosphoranes) react with diamines 0r dihydroxy U S Cl 260/47?260/2? 260/2803 compounds to give phosphorane polyamides or polyesters oI o e I I s s v I e e e e s 1 t' I 260/349, 260/502.4 P, 260/551 P,260/931 y [51] Int. Cl ..C08g 17/133 1 Claim, N0 Drawings PHOSPHORANEPOLYESTERS AND POLYAMIDES This is a division of application, Ser. No.793,630 filed Nov. 12, 1968 now U. S. Pat. No. 3,629,296.

This invention relates in general to novel high molecular weightcompounds having two or more phosphorane linkages per molecule and totheir methods of preparation. More particularly, this invention relatesto the preparation of bis(azidophosphoranes), bis(halophosphoranes) andsuccessively higher molecular weight polyphosphorane condensationproducts and to novel processes for preparing such materials.

Customarily, monomeric and polymeric phosphoranes have been prepared bythe direct reaction of a phosphonylazide with a tertiary phosphine toyield higher molecular weight phosphorane materials. When phosphonyldiazides are reacted directly with phosphines valuable polyphosphoranesare obtained which have utility as fir-retardants and thermally stableplastics. However, such a process, while feasible, is not completelypracticable commercially due to the serious safety problems arising byreason of the extreme shock sensitivity of organic phosphonyl diazidecompounds. Because of this instability of the diazides, commercialpurification of suitable monomers for polyphosphorane production has notbeen possible on a large scale. When impure phosphonyl diazides areutilized as starting materials without purification, the direct reactionwith tertiary phosphines under prior art methods gives polymericproducts with unsatisfactory physical and mechanical properties clue toshort chain length. Thus it has long been desired to prepare thermallystable polyphosphoranes by way of stable easily purified bisphosphoranessuitable for larger scale industrial handling.

it is therefore an object of the present invention to provide a newclass of high molecular weight phosphorus and nitrogencontainingcompounds having two phosphorane linkages per molecule, suitable forpolyphosphorane production and to provide methods for the preparation ofsuch bis-substituted phosphoranes. Being stable such compounds arereadily purified for subsequent use in chemical polymerization andpolycondensation reactions.

it is a further object of this invention to provide a new and novelclass of mixed polyphosphoranes and new polycondensation productstherefrom, and suitable methods for preparing such compounds.

Additional objects and advantages of this invention not specifically setforth above, will become apparent during the course of the discussionwhich follows.

A new stepwise method of preparation of polyphosphoranes has beendiscovered which gives essentially quantitative yields of a new type ofproduct readily purified and suitable for further condensation to higherpolymers. This new method avoids the problem of isolating the highlydangerous phosphonyl dian'des, and instead utilizes new and usefulderivatives having excellent thermal and shock stability:

For a more complete understanding of the nature of this invention thefollowing chemical equations are presented, followed by illustrativeexamples. The basic chernistry involved in this new stepwise method maybest be understood in terms of its application to the preparation ofsimple azidophosphorane and azidothiophosphorane compounds, assummarized in Examples 1 and 3 below. These polymer prototype compoundshave excellent thermal and hydrolytic stability, and by furtherapplication of these methods to compounds having two phosphine groupsper molecule, the bisphosphoranes of the present invention have beenprepared.

The reaction of triphenylphosphine with phenylphosphonyl diazide wasfound to proceed in a stepwise manner under controlled conditions toform the azidophosphorane.

EXAMPLE 1 One mole of purified triphenylphosphine recrystallized fromisopropyl alcohol was dissolved in pyridine and added to a crudesolution of one mole phenylphosphonyl diazide freshly prepared fromphenylphosphonyl dichloride. An exothermic reaction resulted, withevolution of one mole of nitrogen. The solution was concentrated atreduced pressure, and the residue recrystallized. A stable light coloredsolid was obtained with a melting point of 1 10 to 126 C. Furtherpurification and analysis showed the product to bephenylazidophosphonimidotriphenylphosphorane, C H N OP a whitecrystalline solid, mp. l43-l45 C. Upon analysis the compound was foundto contain 14.1 percent phosphorus and had a molecular weight of 438.

Attempts were then made to hydrolyze this compound by adding water to apyridine solution. Initially, the mixture became cloudy and after 30minutes additional water was added causing a white solid to precipitate.After stirring another hour, the mixture was filtered to yield, aftervacuum drying, a white powder, m.p. l48-l50 C. The infrared spectrum ofthis material was identical with that of previously obtainedazidophosphorane, having a strong azide absorption at 2,138 cm".

An additional quantity of the azidophosphorane, about 2.1 g (0.005 mole)was stirred overnight with aqueous sodium hydroxide. Since the samplehad not dissolved in this time, it was heated on a steam bath for 8hours without solution taking place. The sample was filtered, washedwith water, and vacuum dried to yield 2.1 g percent recovery) ofazidophosphorane melting at l40-l45 C. The slightly low and wide meltingpoint indicates some minor impurity although the infi'ared spectrum wasunchanged. Thus, the stable azidophosphorane could not be hydrolyzed tothe corresponding phosphonic acid.

In a similar manner it was found possible to synthesize anazidothiophosphorane by reaction of phenylthiophosphonyl diazide andtriphenyl phosphine.

Here also it has been found that a stepwise reaction ofthiophosphonyldiazide with tertiary phosphine yields products having newand unexpected advantages analgous to results obtained with thephosphonyl derivatives above.

EXAMPLE 11 One mole of purified triphenyl phosphine was dissolved inpyridine. A crude solution of freshly prepared phenylthiophosphonyldiazide in pyridine was slowly added under reflux conditions. Anexothermic reaction resulted and nitrogen was evolved. The product wasan oil with a characteristic infrared azide absorption at 2,141 cm" andwas stable to hydrolysis. The product also showed a strong phosphorus tonitrogen double bond absorption at 1,242 to 1,220 cm", typical ofphenylazidothiophosphonimidotriphenylphosphorane. For furtheridentification the product was reacted with methanol. A solution of 0.02mole of starting material was used. It was necessary to reflux thereaction mixture for about 36 hours in order to complete the reaction(as followed by infrared spectroscopy). After removal of the solvent atreduced pressure and digestion with methanol, 4.5 grams (0.01 mole, 50percent yield) of the desired methoxythiophosphorane was recovered.Recrystallization from methanol and Norite A gave an analytical samplemelting at 121-l23 C. Further purification and analysis showed theproduct to be C,,,H NOP S with 3.17 percent nitrogen, 14.1 percentphosphorus and 7.02 percent sulfur.

Under the new controlled stepwise methods of reaction of the presentinvention for converting phosphines to iahosphoranes, the synthesis ofmonohalophosphoranes proceeds as follows:

The resulting chlorophosphorane is a relatively reactive compound,forming the corresponding acid, on hydrolysis, in quantitative yield.

Subsequent reaction of such mono-halo compounds with sodium azideprovides an alternate source of azidophosphoranes without the necessityof handling the potentially hazardous phosphonyldiazides, which theprior art teaches are necessary starting materials.

The synthesis of a typical haloazidophosphorane was carried out in thefollowing manner.

EXAMPLE Ill One mole of phenylphosphonyl dichloride and one mole ofsodium azide in pyridine solution were stirred at 20 C. for 18 hours.One mole of triphenylphosphine in pyridine was then added. The mixturewas cooled in an ice-water bath during the addition. The exothermicreaction yielded one mole of nitrogen. The mixture was warmed andrefluxed for one hour. The product was found on analysis to bephenylchloroph sphonimidotriphenylphosphorane. The yield was 98 percent.

When a portion of the above solid was mixed with water, first an oil andthan a solid was formed. Recrystallization from methanol and water gavea white crystalline precipitate, with a melting point of 205-206 C.Analysis proved the compound to be C H NO P with 14.6 percent phosphorusand a neutral equivalent of 41 3.

Another portion of the above solid was dissolved in pyridine and treatedwith an equimolar quantity of sodium azide over a period of 6-95 hours,and the reaction mixture poured into water, a white precipitate ofphenylazidophosphonimidotriphenyl phosphorane was obtained. The yieldwas 97 percent of this compound melting at 142-l4 C.

Thus, it was found that under certain conditions a phenylphosphonyldiazide and triphenylphosphine react in a very clearly defined stepwisemanner to yield an azidophosphorane which is thermally stable andresists hydrolysis. The product may be safely stored or purified forfurther reaction to the phenyldiphosphorane. When this method wasextended to certain difunctional phosphines it was found thatquantitative yields of new high molecular weight bisphosphoranes result,the products having pendant azido groups at each end of the molecule.

A typical compound of the present invention, also known as abis(azidophosphorane), may be prepared by direct reaction of crudephenylphosphonyl diazide and a bis(tertiary phosphine). The productexhibits extreme thermal and hydrolytic stability and is readily solublein the usual organic so vents making it relatively simple to purify suchproduct or to carry out further polyconden-sation reactions. Thepreparation of N,N'-[p-pheny1enebis(diphenylphosphoranylidyne)]bis(P-azido-P-phenylphosphonic amide) may be represented as follows:

EXAMPLE IV A solution of one mole of phenylphosphonyl dichloride wastreated with two moles of sodium azide in pyridine, and allowed to standfor 18 hours. A pink solution resulted. To this was added a slurry ofone mole of 1,4 bis( diphenylphosphino) benzene and 50 ml of pyridine.The initial reaction rate was rapid and exothermic and essentiallycomplete in 0.5 hr. The nitrogen collected was found to be essentiallyquantitative. Salts were removed by filtration through a sintered glassfunnel. Removal of the solvent at reduced pressure provided a tackyresidue from which a quantity of the bis(azidophosphorane), m.p. 136-l38C. was isolated. The product was found to have a molecular weight of820, compared to 806 theory by the Neumeyer method.

The infrared spectrum of this material showed a strong azide at 4.72microns as well as the typical phosphorane spectrum from 7-9 microns. Inaddition, there was a marked absence of any absorption at 10.4-10.9microns which might have been ascribed to absorption as a result ofhydrolysis. The infrared spectrum thus resembled the spectrum of purecompound prepared in pyridine. Analysis proved the compound to be C H ON P with 15.5 percent phosphorus.

EXAMPLE V The phenylphosphonyl diazide (2 moles), (Example IV) wasprepared in a benzene pyridine solvent system with a molar ratio of 2:1for the pyridine and phenylphosphonyl dichloride and then reacted withone mole of 4,4-bis(diphenylphosphino)biphenyl in benzene at roomtemperature. For about 1-% hours a stream of nitrogen was evolved. Themixture was filtered and the solvent removed from the filtrate to yieldpale yellow solid with a melting range of l-200 C. The yield of thiscrude product was quantitative. The latter was then washed several timeswith acetone to yield a white solid with a melting point of 210-2l2 C.The infrared spectrum was similar to that of the product made in Example1V including a strong azide absorption in the region of 4.70 microns.Analysis proved the compound to be C.,,,l'l ,,O N,,P with 14.1 percentphosphorus. The overall yield was 75 percent of the biphenylbis(azidophosphorane) also known as N,N-[pBiphenylenebis(diphenylphosphoranylidyne)]- bis- (P-azido-P-phenylphosphonicAmide).

The present invention further includes a process for the preparation ofa second new and previously unknown class of compounds, thebis(halophosphoranes). Such compounds are obtained by a similar stepwisereaction of phosphonyldihalide with one equivalent of sodium azide toyield a monohalophosphonyl azide and subsequent reaction of the productwith a compound having two pendant tertiary phosphine groups permolecule.

The resulting bis(halophosphoranes) may than be further converted intobis-ando compounds by the method of Example IV utilizing 2 moles ofsodium azide per mole of bis( halophosphorane). Suchbis(halophosphoranes) also were found to have chemically active halogengroups which readily undergo condensation reactions with polyamines andpolyglycols to produce phosphorane-bearing polyesters and polyamides ofa new and novel nature.

EXAMPLE v1 One mole of phenylphosphonyl dichloride was reacted with 1.0mole of sodium azide dissolved in dry pyridine by stirring at roomtemperature for 18 hours. Thereafter 0.5 mole of 1,4-bis(diphenylphosphino) benzene in pyridine was added, cool ing themixture in an ice-bath during the addition. The product was obtained byremoval of the solvent and crystallizing. Analysis and infrared spectrashowed the product, to be the bis-( chlorophosphorane), also known asN,N'[p-phenylenebis-( diphenylphosphoranylidyne)]-bis(P-chloro-P-phenylphosphonic amide).

This product was then dissolved in a mixture of benzene and pyridine andstirred with two moles of sodium azide. The rapid foregoing reaction wascomplete in 6 hours. The salts were filtered under nitrogen pressure;and the filtrate concentrated to yield a tan powder. The product wasfound to be identical to the bis( azidophosphorane) of Example IV.

EXAMPLE Vll One mole of the bis(chlorophosphorane), prepared as inExample VI, is dissolved in dimethylformamide. One mole of hydroquinoneis slowly added until the evolution of HCl ceases. The mixture is heatedwith stirring until a thick mass of polymer is obtained. The resultingphosphorane-containing polyester can be vacuum distilled to removedinethylformamide solvent and other volatile materials and yield alinear polymer:

where x indicates the degree of polymerization.

EXAMPLE VIII One mole of bis(chlorophosphorane), prepared as in ExampleVI is dissolved in dimethylsulfoxide. One mole of p-phenylenediamine andtwo moles of triethylarnine are added. Heating at reflux temperature andremoval of the salts and volatiles in vacuo yields a linear polymer:

where x is the degree of polymerization.

The polyesters and polyamides of Examples VII and VIII thus modifiedwith phosphorane linkages possess unique properties as fire retardantmaterials and as modifiers of conventional polyamides and polyesters.

The bis-halo and bis(azidophosphorane) compounds of Examples IV, V andVI are readily soluble in organic polymer solvents such as pyridine,dirnethylformamide and dimethylsulfoxide. Solutions of these purecompounds can then be subjected to further high temperature condensationreactions under optimum controlled conditions not possible in previouslyknown systems which required that the hazardous crude phosphonyl diazidereaction mixtures remain in low boiling point solvents for subsequentpolymerization reactions.

The product of Example IV and V, the bis(azidophosphorane), can beconverted to a tetraphosphorane by reaction with triphenylphosphine inbenzene, toluene, or similar hydrocarbons. When the reaction is carriedout in pyridine, dimethylformamide or dimethylsulfoxide excellent yieldsof tetraphosphorane are obtained.

EXAMPLE IX One mole of triphenylphosphine was dissolved in pyridine and0.5 mole of the bis(azidophosphorane) (Example IV) was added at refluxtemperature. The nitrogen evolved was 96 percent of the theoreticalamount. Removal of the solvent under reduced pressure andrecrystallization yielded 91 percent of light yellow crystals melting atl0ll03 C. Analysis proved the compound to be the tetraphosphorane, C,,I-I O N P with 14.3 percent phosphorus and a molecular weight of 1,250compared to the theoretical value of 1,275.

Subsequent reaction of the bis(azidophosphorane) of Example IV and Vwith l,4-bis(diphenylphosphino) benzene in a variety of solvents such asdimethylformamide, dimethylsulfoxide or hexamethyl phosphoric triamideresulted in unique polyphosphoranes from which numerous fibers and diskswere formed. The products of such controlled polycondensation representa useful class of polyphosphoranes possessing unusual properties. Morethennally stable phosphorane resins are obtained by a careful control ofthe purity of the reacting monomers, and of the stoichiometry of thereacting components. In addition these high temperature stable resinsare more resistant to hydrolyzed phosphonyldiazide compounds in thepolymers. Moreover, the use of more effective polymer solvents makes itpossible to monitor the polymerization reactions through the use ofstandard instrumental control methods until products of specifiedmolecular weights are obtained.

Depending on the choice of reactants these polymeric phosphoranes areuseful as ablative materials and as structural plastics. High molecularweight polymeric phosphoranes provide new thermally stable polymerswhich can be drawn into fibers, fabricated into film and sheetlaminates, or incorporated into varnishes for use as surface coatings.The phosphorus content of these products imparts a high degree ofresistance to combustion, giving them an additional utility asfire-retardant materials, and as polymer modifiers.

While the process of preparation of the bis(halophosphoranes) andbis(azidophosphoranes) of the present invention is conveniently carriedout at room temperature initially, followed by periods of heating at thereflux temperature of the pyridine solvent 1 10 to C.) the reactiontemperatures can range from -20 to C. depending upon the choice ofsolvent and chemical and physical properties of the reactants. Thecompounds of the present invention can be prepared in a variety ofsolvents such as pyridine, acetonitrile, triethylamine, di-n-butylether, benzene, toluene, dimethylformarnide, dirnethylsulfoxide and thelike. Depending upon the particular halogen substituent used, such asfluoride, chloride, bromide and iodide and the number and type ofsubstituents on the phosphorus compounds the reaction time may also varyfrom a few hours to a few days.

It should be noted that the bis(azidophosphorane) of Example IV and VImay be separately isolated and thereafter reacted with a difl'erentbistertiary phosphine than that used for the preparation of thebis-azidophosphoranes. By this technique for the first time it hasbecome possible to vary the properties of the final polyphosphoranes.This is one additional manner in which the stable bis(azidophosphorane)materials of the present invention have a unique utility and lead topolyphosphorane materials of superior properties.

While the present invention has been described in terms of what atpresent are preferred embodiments thereof, it will be understood, ofcourse, that various changes, substitutions, modifications and the likemay be made therein without departing from the true scope of theinvention as defined in the appended claims.

What is claimed is:

l. A high molecular weight linear polymer having the formula where xindicates the degree of polymerization.

UNITED STATES PATENT OFFICE EQTION CE'HFICATE 0F if Patent No. .3 7 742Dated July 4 1 7 Inventor(s) Roger A. Baldwin and Ming T. Cheng It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 1, line 17 "fir-retardants" should read fire-retardants lir le 62"l and 3" should read l to 3 Col. 3,v lines 3 and 4 equation should readC H P(O)N (C H P C H P(O)N=P(C H N I I I Icl c1 lines 31 and 32"phenylchlorophsphonimidotriphenylphosphorane" should read-phenylohlorophosphonimidotriphenylphosphorane line 44 E "142 14" shouldread 142 145 delete "5" line 45 line 60 "so vents" should read solventsline 62 "pol'yoonden-sation" should read polycondensation Col. 6, line 9formula should read C H O N P Signed and sealed this 5th day of December1972.

(SEAL) Attest:

EDWARD MJLETQHERJ'R. ROBERT GOTTSCHALK Attesting Officer v Commissionerof Patents FORM PC4050 uscoMM-Dc 60376-P69 Q U.S. GOVERNMENT PRINTINGOFFICE I 959 O356-334

